06 Ducati ST3 Gas leaking out of gas cap - Ducati.ms - The Ultimate Ducati Forum
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post #1 of 15 (permalink) Old Apr 14th, 2017, 9:16 pm Thread Starter
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06 Ducati ST3 Gas leaking out of gas cap

I haven't messed with the fuel tank other than to replace a blown off line on the fuel bump and that was last year. This issue reared its head when I brought the bike out for spring.m When the gas sloshes around in the fuel tank on bumps or hard acceleration it comes out of the gas cap in a fairly large amount. Enough to get on my jacket and make me smell like gas.


What could be causing this? Is it the seal on the gas tank or is something wrong with the little vent line that goes from the cap area into the tank?


-Barry
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post #2 of 15 (permalink) Old Apr 15th, 2017, 12:22 am
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1) Don't fill the tank up beyond the bottom of the inside of the "neck."

2) Did you completely close the gas cap? After you think you have closed it, remove the key and push down on the center of the cap with your thumb. If it "clicks", then you had not completely closed it.
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post #3 of 15 (permalink) Old Apr 15th, 2017, 8:22 am Thread Starter
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I only filled the tank up 3/4s and it still came out of the gas cap. I will check if its closed or not, but this has happened the two times I have put gas in in since it came out for the season.


-Barry
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post #4 of 15 (permalink) Old Apr 15th, 2017, 8:55 am
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Make sure the vent hose didn't come off the bottom of the cap ring. Also make sure vent hose under tank isn't pinched.


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post #5 of 15 (permalink) Old Apr 15th, 2017, 9:05 am
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+1 on Bill Anderson's? reply, make sure you give the gas cap an extra push down after key removal , if it clicks you should be sealed.
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post #6 of 15 (permalink) Old Apr 15th, 2017, 11:53 am
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Quote:
Originally Posted by flynnmon View Post
+1 on Bill Anderson's? reply, make sure you give the gas cap an extra push down after key removal , if it clicks you should be sealed.


+2. I push the cap down with one hand and turn/remove the key with the other. Had the same issue once before.


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post #7 of 15 (permalink) Old Apr 17th, 2017, 4:56 pm
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I went through this right after picking up my ST3 a few years back. Like others here recommend, don't fill up the tank too close to the tank cap. This is noted in your owner's manual, too. Also, spray some silicone lube on the cap's rubber gasket. You'd be surprised at how much this helps the gasket expand and provide a tighter seal!

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post #8 of 15 (permalink) Old Apr 18th, 2017, 9:07 am
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Quote:
Originally Posted by Tripod View Post
Make sure the vent hose didn't come off the bottom of the cap ring. Also make sure vent hose under tank isn't pinched.
While it could be the cap not completely closed, it's happened before, this comment about the drain / vent lines is more plausible to me if the problem is consistent. It is also a safety issue and should be checked...

Red represents the drain line circuit. If the drain hose came off the nipple at the top of the tank, you would get fuel through the hole under the cap. It is not sealed by the cap, it is an open drain for the flange around the cap. You'll also get water in the tank if it rains or you wash the bike. If the popped off hose fell below the level of fuel in the tank, you'll get fuel out of the drain hose in the lower faring area...

Blue is the vent circuit. I don't see how you'd get fuel out of the cap here unless the hose came off AND your rubber nipple was damaged or missing. This circuit vents to the canister, unless it's bee removed, then it just vents to the atmosphere.


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post #9 of 15 (permalink) Old Apr 19th, 2017, 9:51 pm Thread Starter
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Walks outside presses down on cap... click.... I have had this bike for a year and all of a sudden I can't shut the fuel cap right? SMH
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post #10 of 15 (permalink) Old Apr 20th, 2017, 7:03 am
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I know on my ST4 the rubber seal at the top of the cap is semi-spring loaded and some times will get stuck up I've had the cap apart and lubed it up so the tapper and seal move easier. Yes push down for the click still.

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